An oscillation wavelength of semiconductor laser, which has been frequently used as an image exposing unit is, at present, a long wavelength such as 650 to 820 nm. Accordingly, development of an electrophotographic photosensitive member having high sensitivity to light having such a long wavelength has been advanced.
A phthalocyanine pigment is effective as a charge-generating substance having high sensitivity to light having a wavelength in such a long-wavelength region. In particular, oxytitanium phthalocyanine and gallium phthalocyanine have excellent sensitivity characteristics, and various crystal forms thereof have been reported heretofore.
An electrophotographic photosensitive member using the phthalocyanine pigment has an excellent sensitivity characteristic. However, the electrophotographic photosensitive member involves the following problem. A produced photocarrier is liable to remain on the photosensitive layer of the electrophotographic photosensitive member and is liable to serve as a kind of memory to cause an electric potential variation such as a ghost phenomenon.
Patent Literature 1 reports that addition of a specific organic electron acceptor at the time of an acid pasting process for the phthalocyanine pigment exerts a sensitizing effect. However, the approach involves the following concern and problem. The additive may chemically change, thereby being difficult to transform the additive into a desired crystal form.
In addition, Patent Literature 2 reports the following. When the pigment and a specific organic electron acceptor are subjected to a wet pulverization treatment, the organic electron acceptor is incorporated in a surface of the crystal simultaneously with crystal transformation, and hence the electrophotographic characteristics are improved.
However, the phthalocyanine crystal obtained by the approach does not contain the organic electron acceptor in itself, and the acceptor is merely in a state of being mixed with the crystal or merely adheres to its surface. Accordingly, the approach is identical in constitution and effect to the so-called addition at the time of dispersion in which a specific organic electron acceptor is added at the time of production of a coating liquid for a charge-generating layer.
In addition, Patent Literature 3 discloses that a benzophenone compound is used in an electrophotographic photosensitive member. The literature describes that use of the benzophenone compound exerts a preventing effect on photooxidation of a charge-generating substance and a suppressing effect on an increase in residual potential.
However, none of Patent Literatures 1 to 3 discloses a benzophenone compound substituted with an amino group.